1. Field of the Invention
The present invention relates to a metering device for introducing an operating medium, in particular into an exhaust manifold of an internal combustion engine, having a cooling system for cooling an injector module, in particular, of the metering device, in which the cooling system has a cooling circuit with a cooling fluid, and having at least one cooling device that carries heat out of the cooling circuit.
The present invention further relates to an internal combustion engine having such a metering device.
2. Description of the Prior Art
Known metering devices are used for instance to introduce operating medium, such as an aqueous urea solution used as a reducing agent precursor, into an exhaust manifold of an internal combustion engine. After being introduced into the exhaust gas, the urea solution reacts to form ammonia. The ammonia, in turn, reacts selectively at a so-called SCR (selective catalytic reduction) catalytic converter with nitrogen oxides contained in the exhaust gas of the engine to form molecular nitrogen and water, making denitrification, especially of diesel engine exhaust gases, possible.
To assure safe function of an injector module of the metering device, the injector module being exposed to the hot exhaust gases of the engine, reliable cooling of the injector module is necessary. Typically, the operating medium, such as the aqueous urea solution, also requires cooling in order not to decompose and be made unusable under the influence of the high temperatures from the exhaust manifold.
For this purpose, in the prior art cooling by the operating medium itself, that is, the urea solution, for instance, is proposed. Given a relatively high freezing point of the operating medium, which in the case of the aqueous urea solution is approximately −11° C., such cooling especially in winter cannot be employed, since the operating medium can freeze, and in that condition cooling of the injector module is not possible.
In order nevertheless to enable reliable operation of the engine and rapid introduction of the operating medium even at below-freezing temperatures, the above-described conventional systems are provided with thermally insulated heated lines for the operating medium, which dictates increased production costs for the metering device. In operation of the engine in which the injector module is heated by hot exhaust gases, the thermal insulation of the lines also makes cooling the injector module more difficult.
It is accordingly the object of the present invention to provide an improved metering device and an internal combustion engine having an improved metering device, in which in particular, simple and simultaneously reliable cooling, particularly of an injector module, is possible.